Thorium: The Preferred Nuclear Fuel of the Future

Transcription

1 EIRScience & Technology Thorium: The Preferred Nuclear Fuel of the Future Nuclear engineer Ramtanu Maitra shows, from the case study of India, how the development of thorium fuel cycles will enhance the efficiency and economy of nuclear power plants.* Thorium is an abundant element in nature with multiple ad- mixed oxide (MOX) fuel to breed fissile uranium-233 (Uvantages as a nuclear fuel for future reactors of all types. 233) in a thorium-232 (Th-232) blanket around the core. In the Thorium ore, or monazite, exists in vast amounts in the dark final stage, the fast breeders would use Th-232 and produce U- beach sand of India, Australia, and Brazil. It is also found in 233 for use in new reactors. One main advantage of using a large amounts in Norway, the United States, Canada, and combination of thorium and uranium is related to the proliferation South Africa. Thorium-based fuel cycles have been studied question: There is a significant reduction in the pluto- for about 30 years, but on a much smaller scale than uranium nium content of the spent fuel, compared with what comes or uranium/plutonium cycles. Germany, India, Japan, Russia, out of a conventional uranium-fueled reactor. Just how much the United Kingdom, and the United States have conducted less plutonium is made? The answer depends on exactly how research and development, including irradiating thorium fuel the uranium and thorium are combined. For example, uranium in test reactors to high burn-ups. Several reactors have used and thorium can be mixed homogeneously within each fuel thorium-based fuel, as discussed below. rod, and in this case the amount of plutonium produced is India is by far the nation most committed to study and use roughly halved. But mixing them uniformly is not the only of thorium fuel; no other country has done as much neutron way to combine the two elements, and the mix determines the physics work on thorium as have Indian nuclear scientists. plutonium production. The positive results obtained in this neutron physics work have motivated the Indian nuclear engineers to use thorium- Indian Initiatives based fuels in their current plans for the more advanced reactors To a certain extent, India has completed the first stage of that are now under construction. its nuclear program, putting on line a dozen nuclear power India decided on a three-stage nuclear program back in plants so far, with a few more plants now in the construction the 1950s, when its nuclear power generation program was process. The second stage is as yet realized only by a small set up. In the first stage, natural uranium (U-238) was used in experimental fast breeder reactor (13 megawatts), at Kalpak- pressurized heavy water reactors (PHWRs), of which there kam. Meanwhile, the Indian authorities have approved the are now 12. In the second stage, the plutonium extracted from Department of Atomic Energy s proposal to set up a 500-MW the spent fuel of the PHWRs was scheduled to be used to run prototype of the next-generation fast breeder nuclear power fast breeder reactors. The fast breeders would burn a 70% reactor at Kalpakkam, thereby setting the stage for the com- mercial exploitation of thorium as a fuel source. *Reprinted from 21st Century Science & Technology, Fall India s commitment to switch over to thorium stems, in 64 Science & Technology EIR November 18, 2005

2 Information Service of India USGS India has a plentiful supply of thorium in the rare earth monazite, found in its beach sands. Here workers transport sand to the Rare Earth Processing Plant at Alwaye. Inset is a backscattered electron image of a monazite crystal. Pure thorium is silver in color, but it becomes gray and then black as it oxidizes. part, from its large indigenous thorium supply. India s esti- Abundance of Thorium mated thorium reserves are 290,000 tons, second only to Australia. Although India s embrace of thorium as its future nuclear But the nation s pursuit of thorium, which helps bring fuel is based mostly on necessity, the thorium fuel cycle itself it independence from overseas uranium sources, came about has many attractive features. To begin with, thorium is much for a reason that has nothing to do with its balance of trade. more abundant in nature than uranium. Soil commonly contains India is a nonsignatory of the Nuclear Non-Proliferation an average of around 6 parts per million (ppm) of Treaty (NPT). Hence, India foresaw that it would be con- thorium, three times as much as uranium. strained in the long term by the provisions laid down by the Thorium occurs in several minerals, the most common commercial uranium suppliers, which would jeopardize being the rare earth thorium-phosphate mineral, monazite, India s nuclear power generation program. The 44-member which usually contains from 3 to 9%, and sometimes up to nuclear suppliers group requires that purchasers sign the NPT, 12% thorium oxide. In India, the monazite is found in its and thereby allow enough oversight to ensure that the fuel southern beach sands. (or the plutonium spawned from it) is not used for making nuclear weapons. India began the construction on the facility for reactor physics of the Advanced Heavy Water Reactor (AHWR) last TABLE 1 year. The AHWR will use thorium, the fuel of the future, World Thorium Resources to generate 300 megawatts of electricity, up from its original (economically extractable) design output of 235 megawatts. The reactor will have a life- Reserves time of 100 years, and is scheduled to be built on the campus Country (tons) of India s main nuclear research and development center, the Bhabha Atomic Research Center (BARC) at Trombay. Australia 300,000 The construction of the AHWR will mark the beginning India 290,000 of the third phase of India s nuclear electricity-generation Norway 170,000 program. The fuel for the AHWR will be a hybrid core, partly USA 160,000 thorium/uranium-233, and partly thorium-plutonium. The re- Canada 100,000 actor will be a technology demonstrator for thorium utiliza- South Africa 35,000 tion. According to B. Bhattacharjee, Director of the Bhabha Brazil 16,000 Atomic Research Center, At the international level, the Other countries 95,000 AHWR has been selected for a case study at the IAEA [Inter- World total 1,200,000 national Atomic Energy Agency] for acceptance as per international standards for next-generation reactors. Source: U.S. Geological Survey, Mineral Commodity Summaries, January EIR November 18, 2005 Science & Technology 65

3 Information Service of India The Bhabha Atomic Research Center (BARC) in Trombay, India. Thorium fuel cycles have been intensively studied here, and the design phase of the thorium-fueled Advanced Heavy Water Reactor is under way. At an August meeting in Brussels on emerging reactor designs, two BARC scientists unveiled their design for an Advanced Thorium Breeder reactor (ATBR) that can produce 600 MW of electricity for two years, with no refueling. Th-232 decays very slowly (its half-life is about three The one challenge in using thorium as a fuel is that it times the age of the Earth). Most other thorium isotopes are requires neutrons to start off its fission process. These neu- short-lived and thus much more radioactive than Th-232, but trons can be provided by the conventional fissioning of uranium of negligible quantity. or plutonium fuel mixed into the thorium, or by a In addition to thorium s abundance, all of the mined particle accelerator. Most of the past thorium research has thorium is potentially usable in a reactor, compared with only involved combining thorium with conventional nuclear fuels 0.7% of natural uranium. In other words, thorium has some to provide the neutrons to trigger the fission process. 40 times the amount of energy per unit mass that could be The approach undergoing the most investigation now is a made available, compared with uranium. combination that keeps a uranium-rich seed in the core, From the technological angle, one reason that thorium is separate from a thorium-rich blanket. The chief proponent preferred over enriched uranium is that the breeding of U-233 of this concept was the late Alvin Radkowsky, a nuclear pioneer from thorium is more efficient than the breeding of plutonium who, under the direction of Admiral Hyman Rickover, from U-238. This is so because the thorium fuel creates fewer helped to launch America s Nuclear Navy during the 1950s, non-fissile isotopes. Fuel-cycle designers can take advantage when he was chief scientist of the U.S. Naval Reactors Pro- of this efficiency to decrease the amount of spent fuel per unit gram. Radkowsky, who died in 2002 at age 86, headed up the of energy generated, which reduces the amount of waste to design team that built the first U.S. civilian nuclear reactor at be disposed of. Shippingport, Pennsylvania, and made significant contributions There are some other benefits. For example, thorium oxide, to the commercial nuclear industry during the 1960s the form of thorium used for nuclear power, is a highly and 1970s. stable compound more so than the uranium dioxide that is Although thorium is not fissile like U-235, Th-232 ab- usually employed in today s conventional nuclear fuel. Also, sorbs slow neutrons to produce U-233, which is fissile. In the thermal conductivity of thorium oxide is 10 to 15% higher other words, Th-232 is fertile, like U-238. The Th-232 than that of uranium dioxide, making it easier for heat to flow absorbs a neutron to become Th-233, which decays to protactinium-233 out of the fuel rods used inside a reactor. (Pa-233) and then to fissionable U-233. When the In addition, the melting point of thorium oxide is about irradiated fuel is unloaded from the reactor, the U-233 can be 500 degrees Celsius higher than that of uranium dioxide, separated from the thorium, and then used as fuel in another which gives the reactor an additional safety margin, if there nuclear reactor. Uranium-233 is superior to the conventional is a temporary loss of coolant. nuclear fuels, U-235 and Pu-239, because it has a higher neu- 66 Science & Technology EIR November 18, 2005

4 FIGURE 1 FIGURE 2 Simplified Diagram of the Thorium Fuel Cycle Simplified Diagram of the Uranium Fuel Cycle The neutron trigger to start the thorium cycle can come from the fissioning of conventional nuclear fuels (uranium or plutonium) or an accelerator. When neutrons hit the fertile thorium-232 it decays to the fissile U-233 plus fission fragments (lighter elements) and more neutrons. (Not shown is the short-lived intermediate stage of protactinium-233.) In the conventional uranium fuel cycle, the fuel mix contains fissionable U-235 and fertile U-238. A few fast neutrons are released into the reactor core (for example, from a beryllium source), and when a neutron hits a U-235 nucleus, it splits apart, producing two fission fragments (lighter elements) and two or three new neutrons. Once the fission process is initiated, it can continue by itself in a chain reaction, as the neutrons from each fissioned uranium nucleus trigger new fissions in nearby nuclei. Some of the U-238, when hit by a neutron, decays to plutonium- 239, which is also fissionable. tron yield per neutron absorbed. This means that once it is activated by neutrons from fissile U-235 or Pu-239, thorium s breeding cycle is more efficient than that using U-238 and plutonium. seed and blanket have the same geometry as a normal VVER- The Russian-U.S. Program 100 fuel assembly. As reported by Grae et al. (see note 4), Since the early 1990s, Russia has had a program based at thorium fuel burns 75% of the originally loaded weaponsgrade Moscow s Kurchatov Institute to develop a thorium-uranium plutonium, compared with a 31% burn for mixed oxide fuel. The Russian program involves the U.S. company (MOX) fuel, which is made of a mixture of uranium and Thorium Power, Inc. (founded by Radkowsky), which has plutonium. But unlike MOX, thorium fuel does not produce U.S. government and private funding to design fuel for the more plutonium and has cost advantages over MOX. Grae et conventional Russian VVER-1000 reactors. Unlike the usual al. conclude: nuclear fuel, which uses enriched uranium oxide, the new fuel Thorium fuel offers a promising means to dispose of assembly design has the plutonium in the center as the seed, excess weapons-grade plutonium in Russian VVER-1000 re- in a demountable arrangement, with the thorium and uranium actors. Using the thorium fuel technology, plutonium can be around it as a blanket. disposed of up to three times as fast as MOX at a significantly A normal VVER-1000 fuel assembly has 331 fuel lower cost. Spent thorium fuel would be more proliferationresistant rods, each of 9-millimeter diameter, forming a hexagonal than spent MOX fuel.... [The thorium fuel technolrods, assembly 235-mm wide. The center portion of each assem- ogy] will not require significant and costly reactor modifications. bly is 155-mm across and holds the seed material, consisting Thorium fuel also offers additional benefits in terms of of metallic plutonium-zirconium alloy (about 10% of the reduced weight and volume of spent fuel and therefore lower alloy is plutonium, of which more than 90% is the isotope disposal costs. Pu-239) in the form of 108 twisted three-section rods, which are mm wide, with cladding of zirconium alloy. Four Decades of R&D The blanket consists of uranium-thorium oxide fuel pellets Concepts for advanced reactors based on thorium fuel (in a ratio of uranium to thorium of 1:9, with the uranium cycles include: enriched up to almost 20%) in 228 cladding tubes of zirconium Light Water Reactors. Fuels based on plutonium oxide alloy, 8.4-mm diameter. These pellets are in four layers (PuO 2 ), thorium oxide (ThO 2 ), and/or uranium oxide (UO 2 ) around the center portion. The blanket material achieves 100 particles are arranged in fuel rods. gigawatt-days burn-up. Together as one fuel assembly, the High-Temperature Gas-cooled Reactors (HTGR). These EIR November 18, 2005 Science & Technology 67

5 are of of two kinds: the pebble bed and the prismatic fuel technology for the materials and components. design. Advanced Heavy Water Reactor (AHWR). India is work- The Pebble Bed Modular Reactor (PBMR) originated in ing on this, and like the Canadian CANDU-NG, this 250- Germany, and is now being developed in South Africa and in megawatt-electric (MWe) design is light-water cooled. The China. It can potentially use thorium in its fuel pebbles. main part of the core is subcritical, with Th/U-233 oxide, The Gas Turbine-Modular Helium Reactor (GT-MHR) mixed so that the system is self-sustaining in U-233. A few was developed in the United States by General Atomics using seed regions with conventional MOX fuel will drive the reaction a prismatic fuel. The use of helium as a coolant at high temperature, and give it a negative void coefficient overall. (In other and the relatively small power output per module (600 words, as the reactor heats up, the fission process slows megawatts-thermal), permit direct coupling of the reactor to down.) a gas turbine (a Brayton cycle), resulting in power generation Accelerator Driven Systems (ADS). In accelerator driven at 48 percent thermal efficiency (which is 50% more efficient systems, high-energy neutrons are produced through the than the conventional nuclear reactors in use today). The GT- spallation reaction of high-energy protons from an accelerator MHR core can accommodate a wide range of fuel options, striking target heavy nuclei (lead, lead-bismuth, or other maincluding highly enriched uranium/thorium, U-233/Th, and terials). These neutrons can be directed to a subcritical reactor Pu/Th. The use of highly enriched uranium/thorium fuel was containing thorium, where the neutrons breed U-233 and prodemonstrated in General Atomics Fort St. Vrain reactor in mote its fission. There is therefore the possibility of sustaining Colorado (see below). a fission reaction which can readily be turned off, and used Molten salt reactors. This advanced breeder concept cir- either for power generation or destruction of actinides resulting culates the fuel in molten salt, without any external coolant from the uranium/plutonium fuel cycle. The use of thoculates in the core. The primary circuit runs through a heat exchanger, rium instead of uranium means that fewer new actinides are which transfers the heat from fission to a secondary salt circuit produced in the accelerator-driven system itself. for steam generation. It was studied in depth in the 1960s, and The difficulties, as of now, in developing the thorium is now being revived because of the availability of advanced fuel cycle include the high cost of fuel fabrication. This is The reactor configuration is different from the Radkowsky design in the Russian thorium-burning reac- Thorium Converter Reactor tors. Its ceramic fuel is dispersed in an inert metal matrix covered by Holden s provisional patents. This solid state Ready for Development metal alloy is composed of four materials. The thorium and uranium fuel particles are embedded in the alloy, An attorney-inventor working with Lawrence Berkeley which both slows and moderates the fissioning process. National Laboratory physicists has proposed a small 50- Using the metal as a moderator (instead of the water used megawatt-thermal thorium converter reactor for multiple in other thorium reactor designs) allows the reactor to operuses: producing electricity (15 megawatts), burning up ate in a more energetic neutron spectrum so that its core high-level actinides from spent fuel, and producing low- can have a long life. cost, high-temperature steam (or process industrial heat). The self-regulating reactor is expected to operate for This high-temperature steam can be used for extraction of 10 years without needing refueling. The neutrons to start oil from tar sands, or desalinating, purifying, and cracking it up will be provided by a fusion-driven neutron generator, water. The reactor s fuel matrix can be tuned to provide designed by Dr. Ka-No Leung, head of Plasma and Ion the right output for each particular work process. Source Technology under the Accelerator and Fusion Re- Designed by Charles S. Holden, working with physi- search Division of the Lawrence Berkeley National Labocist Tak Pui Lou, the reactor core is a squat cylinder, about ratory. The alloy and fuel configuration are expected to be 3 meters wide and 1 meter tall. Its size makes it portable, tested at the Advanced Thermal Reactor testing complex at so that it can be brought to a remote work site and supply the Idaho National Lab; computer modelling of the system electricity there without dependence on long-distance will also be done in the national laboratory system. transmission lines. Its small size also allows it to be factory Holden and Pui s company, Thorenco LLC, is now built and transported to its destination, plugged in in a looking for investors to develop a commercial prototype. deep underground containment structure, and put to work Thorenco is based in San Franciso, and can be reached by quickly. The core can be shipped back to the factory when at rusthold@mindspring.com or by telephone 415- the fuel needs to be changed Marjorie Mazel Hecht 68 Science & Technology EIR November 18, 2005

6 Philadelphia Electric Co. partly because of the high radioactivity of U-233, which is always contaminated with traces of U-232; similar problems in recycling thorium because of the highly radioactive Th-228, and some weapons proliferation risk of U-233; and the technical problems (not yet satisfactorily solved) in reprocessing. addition to the United Kingdom, from 1964 to The thorium-uranium fuel was used to breed and feed, so that the U-233 that was formed, replaced the U-235 at about the same rate, and fuel could be left in the reactor for about six years. The General Atomics Peach Bottom high-temperature, graphite-moderated, helium-cooled reactor (HTGR) in the United States operated between 1967 and 1974 at 110-MWt, using highly enriched uranium with thorium. In India, the Kamini 30-kWt experimental neutron-source research reactor started up in 1996 near Kalpakkam, using U-233 which was recovered from thorium-dioxide fuel that had been irradiated in another reactor. The Kamini reactor is adjacent to the 40-MWt Fast Breeder Test Reactor, in which the thorium-dioxide is irradiated. In the Netherlands, an aqueous homogenous suspension reactor has operated at 1 megawatt-thermal for three years. The highly enriched uranium/thorium fuel is circulated in solution, and reprocessing occurs continuously to remove fission products, resulting in a high conversion rate to U-233. General Atomics Peach Bottom reactor, 65 miles southwest of Philadelphia, began commercial operation in This hightemperature, graphite-moderated, helium-cooled reactor operated between 1967 and 1974 at 110-MWt, using highly enriched uranium with thorium. Thorium in Power Reactors The 300-MWe THTR reactor in Germany was developed from the AVR, and operated between 1983 and 1989 with 674,000 pebbles, over half of them containing thorium/highly enriched uranium fuel (the rest of the pebbles were graphite moderator and some neutron absorbers). These pebbles were continuously recycled on load, and on average the fuel passed six times through the core. Fuel fabrication was on an indus- trial scale. The Fort St. Vrain reactor in Colorado was the only commercial thorium-fueled nuclear plant in the United States. Developed from the AVR in Germany, it operated from 1976 to It was a high-temperature (700 C), graphite- moderated, helium-cooled reactor with a thorium/highly enriched uranium fuel, which was designed to operate at 842 megawatts-thermal (330 MWe). The fuel was contained in microspheres of thorium carbide and Th/U-235 carbide, coated with silicon oxide and pyrolytic carbon to retain fission products. Unlike the pebble bed design, the fuel was arranged in hexagonal columns ( prisms ) in an annular configuration. Almost 25 tons of thorium were used in the reactor fuel, achieving a 170,000-megawatt-days burn-up. Thorium-based fuel for Pressurized Water Reactors Thorium Fuel Operating Experience Between 1967 and 1988, the AVR experimental pebble bed reactor at Jülich, Germany, operated for more than 750 weeks at 15 megawatts-electric, about 95 percent of the time with thorium-based fuel. The fuel used consisted of about 100,000 billiard ball-size fuel elements. Overall, a total of (PWRs) was investigated at the Shippingport reactor in the 1,360 kilograms of thorium was used, mixed with highly enriched United States (the first U.S. commercial reactor, started up in uranium (HEU). Maximum burn-ups of 150, ), using both U-235 and plutonium as the initial fissile megawatt-days were achieved. Thorium fuel elements with a material. It was concluded that thorium would not signifi- 10:1 ratio of thorium to highly enriched uranium were irradi- cantly affect operating strategies or core margins. The light ated in the 20-megawatts-thermal (MWt) Dragon reactor at water breeder reactor (LWBR) concept was also successfully Winfrith, United Kingdom, for 741 full-power days. Dragon tested at Shippingport, from 1977 to 1982, with thorium and was run as a cooperative project of the Organization of Economic U-233 fuel clad with zircaloy, using the seed/blanket Cooperation and Development and Euratom, involv- concept. ing Austria, Denmark, Sweden, Norway, and Switzerland, in Another reactor type, the 60-MWe Lingen Boiling Water EIR November 18, 2005 Science & Technology 69

7 FIGURE 3 Cutaway View of the VVER-1000 (1) Horizontal steam generator (2) Reactor coolant pump (3) Containment building Source: Argonne National Laboratory (4) Refueling crane (5) Control rod drive assemblies (6) Reactor vessel The 1,000-MW VVER, Russia s conventional reactor design is shown here in its third generation version. It is a pressurized light-water-cooled and -moderated reactor, similar to Western pressurized water reactors in operation and safety standards. The Thorium Power/Radkowsky design would modify the core for a thorium fuel cycle that would burn up weapons plutonium. Reactor (BWR) in Germany also utilized fuel test elements that were thorium-plutonium based. Proliferation Issues In the early days of the civilian nuclear program, the Acheson-Lilienthal Report in 1946 warned of the connection between civilian nuclear power and nuclear weapons, and concluded that the world could not rely on safeguards alone to protect complying states against the hazards of violations and evasions -illicit nuclear weapons. Acheson-Lilienthal proposed international controls over nuclear power, but also considered possible technical innovations that would make it harder to divert nuclear materials into bomb-making. The thorium fuel cycle is one such technical innovation as yet untapped. A 1998 paper by Radkowsky and Galparin (see note 8) describes the most advanced work in developing a practical nuclear power system that could be made more proliferation resistant than conventional reactors and fuel cycles. Based on a thorium fuel cycle, it has the potential to reduce the amount of plutonium generated per gigawatt-year by a factor of five, compared to conventional uranium-fueled reactors. It would also make the generated plutonium and uranium-233 much more difficult to use for producing bomb material. Heightened current concerns about preventing the spread of bomb-making materials, have led to an increase in interest in developing thorium-based fuels. The U.S. Department of Energy has funded Radkowsky s company (Thorium Power) and its partners in their tests with Russian reactors, as well as three other efforts (two national laboratories, two fuel fabrication companies, and a consortium of three universities). This research is geared to designing a thorium fuel system that will fit with conventional reactors. (See box, p. 68, for another thorium design.) There is also a new company, Novastar Resources, that is buying up thorium mines in anticipation of thorium-fueled reactors in the future. The proliferation potential of the light water reactor fuel cycle may be significantly reduced by using thorium as a fertile component of the nuclear fuel, as noted above. The main challenge of thorium utilization is to design a core and a fuel cycle that would be proliferation-resistant and economically feasible. This challenge is met by the Radkowsky Thorium Reactor concept. So far, the concept has been applied to a Russian design of a 1,000-MW pressurized water reactor VVER, designated as VVERT. The main results of the preliminary reference design are as follows: The amount of plutonium contained in the Radkowsky Thorium Reactor spent fuel stockpile is reduced by 80%, in comparison with a VVER of conventional design. The isotopic composition of the reactor s plutonium greatly increases the probability of pre-initiation and yield degradation of a nuclear explosion. An extremely large Pu- 238 content causes correspondingly large heat emission, which would complicate the design of an explosive device based on plutonium from this reactor. The economic incentive to reprocess and reuse the fissile component of the Radkowsky Thorium Reactor spent fuel is also decreased. The once-through cycle is economically optimal for its core and cycle. To reiterate the proliferation difficulties: the replacement 70 Science & Technology EIR November 18, 2005

8 FIGURE 4 (A) VVER Fuel Rod Assembly (B) Design for Thorium Seed/Blanket Assembly Nukeworker.com Thorium Power, Inc. Radkowsky design for the thorium seed/blanket assembly. The seed fuel is the inner part of the fuel rod (three-sectioned), and the blanket fuel is the outer part. The thorium fuel assembly is designed to replace the current fuel assembly, without requiring a major design rehaul. of a standard (uranium-based) fuel for nuclear reactors of Sources current generation by the Radkowsky Thorium Reactor fuel 1. Benedict, T. H. Pigford, and H.W. Levi, Thorium in Nuclear will provide a strong barrier for nuclear weapon prolifera- Chemical Engineering (2nd Ed.), Chapter 6. (New York: McGraw-Hill) tion. This barrier, in combination with existing safeguard pp measures and procedures, is adequate to unambiguously dis- 2. EIA, The Role of Thorium in Nuclear Energy. (Washington, associate civilian nuclear power from military nuclear D.C.: Energy Information Administration/Uranium Industry Annual, power. 1996), pp. ix-xvii. 3. R.L. Garwin and G. Charpak, Megawatts and Megatons (Chicago: Other scientists point out that even if a terrorist group University of Chicago Press). wanted to use the blanket plutonium for making a bomb, 4. Seth Grae, Dr. Alexei G. Morozov, and Dr. Andrey Mushakov, the process of extracting it from thorium fuel would be Thorium Fuel As a Superior Approach to Disposing of Excess more difficult than removing it from conventional spent Weapons-grade Plutonium in Russian VVER-1000 Reactors, Nuclear fuel. This is because the spent blanket fuel from a thorium Future (Jan.-Feb. 2005). (Journal of the Institute of Nuclear Engineers and the British Nuclear Energy Society). fuel cycle would contain uranium-232, which over time 5. IAEA, Thorium-based Fuel Options for the Generation of Elecdecays into isotopes that emit high-energy gamma rays. To tricity: Developments in the 1990s, IAEA-TECDOC (Vienna: extract the plutonium from this spent fuel would require International Atomic Energy Agency, May). significantly more radiation shielding plus additional reentist 6. M.S. Kazimi, Thorium Fuel for Nuclear Energy, American Sci- (Sept.-Oct.). motely operated equipment in order to reprocess it for weap- 7. J. Carson Mark, Explosive Properties of Reactor-grade Plutoons use, making a daunting task even more difficult. It nium, Science and Global Security, Vol. 4, pp would also be more complicated to separate the fissionable 8. A. Radkowsky and A. Galperin, The Nonproliferative Light Water U-233 from uranium-238, because of the highly radioactive Reactor: A New Approach to Light Water Reactor Core Technology, products present. Nuclear Technology, Vol. 124, pp (Dec.). 9. S. Shwageraus, X. Zhao, M. Driscoll, P. Hejzlar, M.S. Kazimi, and Overall, the development of thorium fuel cycles makes J.S. Herring. Micro-heterogeneous Thoria-urania Fuels for Pressurized sense for the future, for advancing the efficiency and econ- Water Reactors, Nuclear Technology (in press). omy of nuclear power plants, ease of recycling, and making 10. Richard Wilson, How To Have Nuclear Power Without Nuclear it more difficult to divert radioactive materials for weapons. Weapons, Bulletin of the Atomic Scientists (Nov.). EIR November 18, 2005 Science & Technology 71